The Moon

Moon facts

• 384 400 km

  Mean distance

  On average the Moon is 384,400 km away. Almost all the planets of the Solar System would fit side by side in that gap. Light takes about 1.3 seconds to reach us.

• 3 475 km

  Diameter

  The Moon is about a quarter of Earth's diameter. It is the fifth-largest moon in the Solar System.

• 1/6

  Gravity

  You weigh about one sixth of your Earth weight on the Moon: a 60 kg person would weigh like 10 kg.

• 29,5 d

  The cycle of phases

  On average 29.5 days pass between two new Moons (the synodic month). A full orbit relative to the stars takes 27.3 days: the difference comes from Earth moving along its own orbit meanwhile.

• ≈ 59%

  One face, but not quite

  The Moon spins once per orbit, so it always shows us the same face. Thanks to small wobbles (librations), about 59% of its surface can be seen from Earth over time.

• 127 / −173 °C

  Temperature swing

  With no atmosphere to hold heat, the surface reaches about 127 °C in sunlight and drops to about −173 °C in darkness. Permanently shadowed polar craters are colder still.

• ≈ 3,8 cm

  Moving away every year

  By timing laser light bounced off mirrors left by the Apollo missions, we know the Moon is moving away from Earth by about 3.8 cm a year.

• 4,5 Gyr

  Born from an impact

  The leading hypothesis: about 4.5 billion years ago a Mars-sized body struck the young Earth, and the debris came together to form the Moon.

• H₂O

  There is water ice

  Water ice exists in polar craters that sunlight never reaches. In 2020 water was also confirmed on the sunlit surface, in Clavius crater.

• 382 kg

  Pieces of the Moon on Earth

  The Apollo missions brought back 382 kg of lunar rocks and soil, still studied today in laboratories around the world.

• 12

  People on the Moon

  Twelve astronauts have walked on the Moon, all on Apollo missions between 1969 and 1972.

• ≈ 14%

  Supermoon

  The Moon's orbit is an ellipse: a full Moon near perigee looks up to about 14% bigger and 30% brighter than one at apogee. With the naked eye the difference is hard to notice.

• Leonardo

  Earthshine

  Near new Moon you can faintly see the dark part too: it is lit by sunlight reflected off Earth. The correct explanation already appears in Leonardo da Vinci's notes.

• ≠ lato oscuro

  The far side is not dark

  The face we never see gets as much sunlight as the near side: it is hidden, not dark. When we have a new Moon, the far side is in full daylight.

Milestones of exploration

1. September 13, 1959/URSS / USSR

   Luna 2

   First human-made object to reach the Moon (impact).

2. February 3, 1966/URSS / USSR

   Luna 9

   First soft landing and first pictures from the surface.

3. December 24, 1968/NASA

   Apollo 8

   First humans to orbit the Moon.

4. July 20, 1969/NASA

   Apollo 11

   Neil Armstrong and Buzz Aldrin become the first people to walk on the Moon.

5. December 11, 1972/NASA

   Apollo 17

   The last mission with astronauts on the surface, so far.

6. January 3, 2019/CNSA

   Chang'e 4

   First landing on the far side of the Moon.

7. August 23, 2023/ISRO

   Chandrayaan-3

   First landing near the lunar south pole.

8. June 25, 2024/CNSA

   Chang'e 6

   First samples returned to Earth from the far side.